linux-kernel - Re: [PATCH][RESEND][ISDN] fix possible NULL deref on low memory condition in capidrv.c::send

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Date:	Mon, 6 Aug 2007 14:05:51 +0200
From:	Karsten Keil <kkeil@...e.de>
To:	Jesper Juhl <jesper.juhl@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	isdn4linux@...tserv.isdn4linux.de, Carsten Paeth <calle@...le.de>,
	Karsten Keil <kkeil@...e.de>,
	Kai Germaschewski <kai.germaschewski@....de>,
	Kai Germaschewski <kai@...maschewski.name>
Subject: Re: [PATCH][RESEND][ISDN] fix possible NULL deref on low memory condition in capidrv.c::send_message()

On Sat, Aug 04, 2007 at 08:31:37PM +0200, Jesper Juhl wrote:
> (first send: Monday 25 June 2007, resending due to no response)
> (resending again since there has still been no response)
> 
> 
> If we fail to allocate an skb in 
> drivers/isdn/capi/capidrv.c::send_message(), then we'll end up 
> dereferencing a NULL pointer.
> Since out of memory conditions are not unheard of, I believe it 
> is better to print a error message and just return rather than 
> bring down the whole kernel. 
> Sure, doing this may upset some application, but that's still 
> better than crashing the whole system.
> 
> (ps. please Cc me on replies from the isdn4linux list since I'm not subscribed 
>  there)
> 
> 
> Signed-off-by: Jesper Juhl <jesper.juhl@...il.com>

Acked-by: Karsten Keil <kkeil@...e.de>

> ---
> 
>  drivers/isdn/capi/capidrv.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/isdn/capi/capidrv.c b/drivers/isdn/capi/capidrv.c
> index 23b6f7b..476012b 100644
> --- a/drivers/isdn/capi/capidrv.c
> +++ b/drivers/isdn/capi/capidrv.c
> @@ -506,9 +506,14 @@ static void send_message(capidrv_contr * card, _cmsg * cmsg)
>  {
>  	struct sk_buff *skb;
>  	size_t len;
> +
>  	capi_cmsg2message(cmsg, cmsg->buf);
>  	len = CAPIMSG_LEN(cmsg->buf);
>  	skb = alloc_skb(len, GFP_ATOMIC);
> +	if (!skb) {
> +		printk(KERN_ERR "capidrv::send_message: can't allocate mem\n");
> +		return;
> +	}
>  	memcpy(skb_put(skb, len), cmsg->buf, len);
>  	if (capi20_put_message(&global.ap, skb) != CAPI_NOERROR)
>  		kfree_skb(skb);
> 
> 
> -
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-- 
Karsten Keil
SuSE Labs
ISDN and VOIP development
SUSE LINUX Products GmbH, Maxfeldstr.5 90409 Nuernberg, GF: Markus Rex, HRB 16746 (AG Nuernberg)
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